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package com.oracle.truffle.api.library.test.examples;

import static org.junit.Assert.assertEquals;

import org.junit.Test;

import com.oracle.truffle.api.CallTarget;
import com.oracle.truffle.api.dsl.NodeChild;
import com.oracle.truffle.api.dsl.Specialization;
import com.oracle.truffle.api.frame.VirtualFrame;
import com.oracle.truffle.api.library.test.examples.ArrayStrategy1Factory.ArrayReadNodeGen;
import com.oracle.truffle.api.nodes.Node;
import com.oracle.truffle.api.nodes.RootNode;

/**
 * Runnable source code for array strategy1 from the
 * <a href="https://github.com/oracle/graal/blob/master/truffle/docs/TruffleLibaries.md">motivation
 * article</a>.
 */
public class ArrayStrategy1 {

    final class BufferArray {
        int length;
        int[] buffer;

        BufferArray(int length) {
            this.length = length;
            this.buffer = new int[length];
        }
    }

    final class SequenceArray {
        final int start;
        final int stride;
        final int length;

        SequenceArray(int start, int stride, int length) {
            this.start = start;
            this.stride = stride;
            this.length = length;
        }
    }

    abstract static class ExpressionNode extends Node {
        abstract Object execute(VirtualFrame frame);
    }

    @NodeChild
    @NodeChild
    abstract static class ArrayReadNode extends ExpressionNode {

        @Specialization
        int doBuffer(BufferArray array, int index) {
            return array.buffer[index];
        }

        @Specialization
        int doSequence(SequenceArray seq, int index) {
            return seq.start + seq.stride * index;
        }
    }

    static final class ArgumentNode extends ExpressionNode {
        private final int index;

        ArgumentNode(int index) {
            this.index = index;
        }

        @Override
        Object execute(VirtualFrame frame) {
            return frame.getArguments()[index];
        }
    }

    static final class ExampleRootNode extends RootNode {

        @Child private ExpressionNode node;

        ExampleRootNode(ExpressionNode node) {
            super(null);
            this.node = node;
        }

        @Override
        public Object execute(VirtualFrame frame) {
            return node.execute(frame);
        }

    }

    @Test
    public void runExample() {
        ArrayReadNode read = ArrayReadNodeGen.create(new ArgumentNode(0), new ArgumentNode(1));
        CallTarget target = new ExampleRootNode(read).getCallTarget();

        assertEquals(3, target.call(new SequenceArray(1, 2, 3), 1));
        assertEquals(0, target.call(new BufferArray(2), 1));
    }

}
